import java.util.LinkedList;
import java.util.Queue;

public class TestBinaryTree {

    static class TreeNode {
        public char val;//存数据
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }


    // 创建一棵二叉树 返回这棵树的根节点
    public TreeNode createBinaryTree() {
        TreeNode node1 = new TreeNode('1');
        TreeNode node2 = new TreeNode('2');
        TreeNode node3 = new TreeNode('3');
        TreeNode node4 = new TreeNode('4');
        TreeNode node5 = new TreeNode('5');
        TreeNode node6 = new TreeNode('6');
        TreeNode root = node1;
        node1.left = node2;
        node2.left = node3;
        node1.right = node4;
        node4.left = node5;
        node5.right = node6;
        return node1;
    }
//    public TreeNode createTree() {
//        TreeNode A = new TreeNode('A');
//        TreeNode B = new TreeNode('B');
//        TreeNode C = new TreeNode('C');
//        TreeNode D = new TreeNode('D');
//        TreeNode E = new TreeNode('E');
//        TreeNode F = new TreeNode('F');
//        TreeNode G = new TreeNode('G');
//        //TreeNode H = new TreeNode('H');
//
//        A.left = B;
//        A.right = C;
//        B.left = D;
//        B.right = E;
//        C.left = F;
//        C.right = G;
//        //E.right = H;
//        return A;
//    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root == null){
            return;
        }
        System.out.print(root.val + " ");
        postOrder(root.left);
        postOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if(root == null){
            return;
        }
        postOrder(root.left);
        System.out.print(root.val + " ");
        postOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if(root == null){
            return;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val + " ");
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    void size(TreeNode root) {
        if(root == null){
            return;
        }
        nodeSize++;
        size(root.left);
        size(root.right);
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if(root == null){
            return 0;
        }
        int ret = size2(root.left) + size2(root.right) + 1;
        return ret;
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    void getLeafNodeCount1(TreeNode root) {
        if(root == null){
            return;
        }
        if(root.left == null && root.right ==null) {
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if (root == null) {
            return 0;
        }
        if (root.left == null && root.right == null) {
            return 1;
        }
        return getLeafNodeCount2(root.left) + getLeafNodeCount2(root.right);
    }
    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if(root == null){
            return 0;
        }
        if(k == 1){
            return 1;
        }
        return getKLevelNodeCount(root.right,k-1) + getKLevelNodeCount(root.left,k-1);
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
       if(root == null){
           return 0;
       }
       int leftHeight = getHeight(root.left);
       int rightHeight = getHeight(root.right);
       return getHeight(root.left) > getHeight(root.right) ? leftHeight + 1 : rightHeight + 1;
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if(root == null){
            return null;
        }
        if(root.val == val){
            return root;
        }
        TreeNode ret = find(root.left,val);
        if(ret != null) {
            return ret;
        }

        ret = find(root.right,val);
        if(ret != null) {
            return ret;
        }
        return null;
    }

    //层序遍历void levelOrder(TreeNode root) {
    //        Queue<TreeNode> queue = new LinkedList<>();
    //        if(root == null){
    //            return;
    //        }
    //        queue.offer(root);
    //        while(!queue.isEmpty()){
    //            TreeNode cur = queue.poll();
    //            System.out.print(cur.val + " ");
    //            if(cur.left != null){
    //                queue.offer(cur.left);
    //            }
    //            if(cur.right != null){
    //                queue.offer(cur.right);
    //            }
    //        }
    //        System.out.println();
    //    }



    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while(!queue.isEmpty()){
            TreeNode cur = queue.poll();
            if(cur == null){
                break;
            }
            queue.offer(cur.left);
            queue.offer(cur.right);
        }
        while(!queue.isEmpty()){
            TreeNode node = queue.peek();
            if(node == null){
                queue.poll();
            }else {
                return false;
            }
        }
        return true;
    }
}